Variation in air conditioner power readings - can anyone explain?

I've attached a screenshot of a multigraph showing outside temp (yellow line) and power consumption by my air conditioner (blue bars). I'm wondering if anyone can explain why the air conditioner power consumption is varying with the temperature.

What I would expect is that the air conditioning is on or off. 4000 W or 0 W.

I would expect to see it on more on hot days and off more at night and on cool days.

Instead what I am seeing is that, when the unit is on the power consumption varies between about 3700 W and 4500 W, higher when the temp is higher, lower when the temp is lower. And it will actually climb while running if the temperature is climbing, and fall while running if the temperature if falling.

Setup is: emonTx v3.4 with CT from the OEM Shop reading the current to the air conditioner, plugged into input 4 of the emonTx. AC-AC adapter measuring voltage. USA=TRUE.

The air conditioner is a central AC unit, Carrier 24ABB (full model number on my manual says Carrier 24abb360a320).

 

 

pb66's picture

Re: Variation in air conditioner power readings - can anyone explain?

I guess the gas will probably need more effort to compress at higher temperatures so the draw of the compressor motor will increase as well as its duty cycle.

Paul

dBC's picture

Re: Variation in air conditioner power readings - can anyone explain?

Looks to me like it might have an inverter in it:  https://en.wikipedia.org/wiki/Air_conditioner_inverter

Robert Wall's picture

Re: Variation in air conditioner power readings - can anyone explain?

No inverter/variable speed drive is mentioned (nor hinted at) in the manual I looked at, so I'd go with Paul's suggestion. It's not the resistance of the motor windings, as I'd expect that to increase with temperature and thus lower the current.

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